Buggy code:
public class Button extends Control { String text = "" ; String message = "" ; Image image ; Image image2 ; Image disabledImage ; ImageList imageList ; boolean ignoreMouse ; boolean grayed ; static final int MARGIN = 4 ; static final int CHECK_WIDTH ; static final int CHECK_HEIGHT ; static final int ICON_WIDTH = 128 ; static final int ICON_HEIGHT = 128 ; static final boolean COMMAND_LINK = false ; static final int ButtonProc ; static final TCHAR ButtonClass = new TCHAR ( 0 , "BUTTON" , true ) ; public Button ( Composite parent , int style ) { } void _setImage ( Image image ) { } void _setText ( String text ) { } public void addSelectionListener ( SelectionListener listener ) { } int callWindowProc ( int hwnd , int msg , int wParam , int lParam ) { } static int checkStyle ( int style ) { <START_BUG> style = checkBits ( style , PUSH , ARROW , CHECK , RADIO , TOGGLE , ( Button . COMMAND_LINK ? SWT . COMMAND : 0 ) ) ; <END_BUG> if ( ( style & ( ( SWT . PUSH ) | ( SWT . TOGGLE ) ) ) != 0 ) { return checkBits ( style , CENTER , LEFT , RIGHT , 0 , 0 , 0 ) ; } if ( ( style & ( ( SWT . CHECK ) | ( SWT . RADIO ) ) ) != 0 ) { return checkBits ( style , LEFT , RIGHT , CENTER , 0 , 0 , 0 ) ; } if ( ( style & ( SWT . ARROW ) ) != 0 ) { style |= SWT . NO_FOCUS ; return checkBits ( style , UP , DOWN , LEFT , RIGHT , 0 , 0 ) ; } return style ; } void click ( ) { } int computeLeftMargin ( ) { } public Point computeSize ( int wHint , int hHint , boolean changed ) { } void createHandle ( ) { } int defaultBackground ( ) { } int defaultForeground ( ) { } void enableWidget ( boolean enabled ) { } public int getAlignment ( ) { } boolean getDefault ( ) { } public boolean getGrayed ( ) { } public Image getImage ( ) { } String getMessage ( ) { } String getNameText ( ) { } public boolean getSelection ( ) { } public String getText ( ) { } boolean isTabItem ( ) { } boolean mnemonicHit ( char ch ) { } boolean mnemonicMatch ( char key ) { } void releaseWidget ( ) { } public void removeSelectionListener ( SelectionListener listener ) { } void selectRadio ( ) { } public void setAlignment ( int alignment ) { } void setDefault ( boolean value ) { } boolean setFixedFocus ( ) { } public void setImage ( Image image ) { } public void setGrayed ( boolean grayed ) { } void setMessage ( String message ) { } boolean setRadioFocus ( boolean tabbing ) { } boolean setRadioSelection ( boolean value ) { } boolean setSavedFocus ( ) { } public void setSelection ( boolean selected ) { } public void setText ( String string ) { } void updateSelection ( int flags ) { } int widgetStyle ( ) { } TCHAR windowClass ( ) { } int windowProc ( ) { } LRESULT WM_ERASEBKGND ( int wParam , int lParam ) { } LRESULT WM_GETDLGCODE ( int wParam , int lParam ) { } LRESULT WM_KILLFOCUS ( int wParam , int lParam ) { } LRESULT WM_LBUTTONDOWN ( int wParam , int lParam ) { } LRESULT WM_LBUTTONUP ( int wParam , int lParam ) { } LRESULT WM_SETFOCUS ( int wParam , int lParam ) { } LRESULT WM_SIZE ( int wParam , int lParam ) { } LRESULT WM_SYSCOLORCHANGE ( int wParam , int lParam ) { } LRESULT WM_UPDATEUISTATE ( int wParam , int lParam ) { } LRESULT wmCommandChild ( int wParam , int lParam ) { } LRESULT wmColorChild ( int wParam , int lParam ) { } LRESULT wmDrawChild ( int wParam , int lParam ) { } }

Fix:
style = checkBits ( style , PUSH , ARROW , CHECK , RADIO , TOGGLE , 0 ) ;